1. Technical Field
The present invention relates to a linear vibrator.
2. Description of the Related Art
A linear vibrator is a part that converts electrical energy into mechanical vibrations by using the principle of generating electromagnetic forces, and is commonly installed in a mobile phone to generate a soundless vibrating alert. With the rapid expansion of mobile phone markets and increased functionalities added to the mobile phone, mobile phone parts are increasingly required to be smaller and better. As a result, there has been an increased demand for the development of a new structure of linear vibrator that can improve the shortcoming of conventional linear vibrators and effectively improve the quality.
As mobile phones having a bigger LCD screen have become popular for the past few years, there have been an increasing number of mobile phones adopting a touch-screen method, by which vibration is generated when the screen is touched. Touch-screens particularly require that the linear vibrator has a greater durability due to a greater frequency of generating vibration in response to the touch compared to the vibration bell for incoming calls and that the vibration has a faster response to the touch made on the touch screen, in order to provide a user a great satisfaction from sensing the vibration when touching the touch screen.
The conventional linear vibrator commonly used in mobile phones generates a rotational force to cause mechanical vibrations by rotating an eccentric (unbalanced) weight. The rotational force is generated by supplying an electric current to the coil of a rotor through point contacts between a brush and a commutator by way of rectifying action.
However, the brush type structure using such commutator has a shorter motor life due to mechanical friction and electrical sparks, which cause wear and black powder, between the brush and the commutator when the motor rotates. Moreover, when voltage is supplied to the motor, it takes time to reach the target amount of vibration by the rotational inertia of the motor. Thus, it is difficult to implement the vibration appropriate for touchscreen phones.
Commonly used to overcome the drawbacks of shorter life time and slower responsiveness in the vibrating functionality of touchscreen phones is a linear vibrator. The linear vibrator does not use the principle of rotating of a motor but uses an electromagnetic force having a predetermined resonant frequency to generate vibrations by use of a spring installed in the vibrator and a mass coupled to the spring. Here, the electromagnetic force is generated through an interactive reaction between a magnet, which is placed on the moving mass, and a direct or alternating current having a particular frequency flowing through a coil, which is placed on a stationary part.
The linear vibrator commonly employed in a high-end touchscreen phone is placed generally near the corner of the mobile phone to generate the vibration in a direction perpendicular to the LCD screen. The linear vibrator may have dimensions of 10 mm in external diameter and 4 mm in thickness. However, in the linear vibrator, which is designed to vibrate in the perpendicular direction, the mass installed in the linear vibrator is required to secure a vertical displacement within 4 mm of space so as to generate vibrations, so that the space limitation becomes much significant and increasing the amount of vibration may be restricted.